6 wheel design question

[alfa147x]

We are making a robot and i am in charge of the Inventor drawings;
The 6 wheel design is when 3 wheels are put in a line parallel to another set of 3 wheels all of them are driven with 2 motors (each side has one) all are powered

the middle wheel on each set is lowered about an 1\8 of an inch, this allows the bot to rotate 360 on its footstep

I was wondering does the bot need to balanced completely? or would it not matter? the bot should weigh a total of about 98 pounds and with our lift on the front it seems as though the CG would be low but a bit in the front, should we balance it?

 

[CycloWizard]

It depends on how fast it turns, how high the center of gravity is, and how wide the footprint is. Chances are that a slight imbalance wouldn't matter, but a major one could be very important, especially if it rotates very quickly, if the footprint is narrow, and/or the center of gravity is high.

 

[alfa147x]

Originally posted by: CycloWizard
It depends on how fast it turns, how high the center of gravity is, and how wide the footprint is. Chances are that a slight imbalance wouldn't matter, but a major one could be very important, especially if it rotates very quickly, if the footprint is narrow, and/or the center of gravity is high.

Ok ill keep that in mind its the battery that is the heaviest and ill put it near the back that way it will off set the weight for the lift

Thanks !

 

[jagec]

How fast is this robot? How rough is the terrain over which it will traverse? If it's relatively slow (running speed), isn't going over really rough terrain, and has a wide enough footprint, as long as the CG is fairly low you can have pretty significant imbalances without seriously affecting it. Weight toward the middle or slightly toward the back (I assume this lift has to, well, lift something) would make it a bit more nimble than having heavy weights far toward the front and/or back. Weight toward the sides probably isn't a huge deal except on inclines, but you might get some pulling toward one side or the other if it's too uneven. Weight up high can be a little tricky because sudden acceleration, deceleration, or turning can cause it to tip over, and inclines are risky as well.

 

[alfa147x]

its about 3\4 meters wide and long
according to calculations it should go 12ft\sec on the second speed of the trany it should be 6ft\sec (torque)

 

[jagec]

Originally posted by: alfa147x
its about 3\4 meters wide and long
according to calculations it should go 12ft\sec on the second speed of the trany it should be 6ft\sec (torque)

Then I'm guessing that you won't have many problems unless the CG is quite high. A low polar moment of inertia would be nice for fast pivots and agility, so try to get that weight as close to the center as possible, even if you have to raise it up a little bit to do so. Batteries generally should be close to the middle and as low as possible.

 

[alfa147x]

Originally posted by: jagec

Originally posted by: alfa147x
its about 3\4 meters wide and long
according to calculations it should go 12ft\sec on the second speed of the trany it should be 6ft\sec (torque)

Then I'm guessing that you won't have many problems unless the CG is quite high. A low polar moment of inertia would be nice for fast pivots and agility, so try to get that weight as close to the center as possible, even if you have to raise it up a little bit to do so. Batteries generally should be close to the middle and as low as possible.

Okay thanks!
Wow this is the first time I ventured into the deep realms of this side of the forums;

 

[Throckmorton]

It matters because the side with more weight will have a smaller proportion of force on the middle wheels. That will make it turn better in one direction.
I think